I haven't noticed the same behaviour with MyFaces but when running something like ACE Showcase with Mojarra, the jsf.js file is loaded twice. The reason is that the h:commandLink components used on the page will render out an inline reference to the file if Mojarra determines it's necessary. You can see it in the CommandLinkRenderer class:


    @Override
    public void encodeBegin(FacesContext context, UIComponent component)
          throws IOException {

        rendererParamsNotNull(context, component);

        if (!shouldEncode(component)) {
            return;
        }

        boolean componentDisabled =
              Boolean.TRUE.equals(component.getAttributes().get("disabled"));

        String formClientId = RenderKitUtils.getFormClientId(component, context);

        if (componentDisabled || formClientId == null) {
            renderAsDisabled(context, component);
        } else {
            RenderKitUtils.renderJsfJs(context);
            renderAsActive(context, component);
        }

    }

In the method, it attempt to do a check to see if jsf.js is already there (which we do in the BridgeSetup) but it presumably fails that check and renders out an inline script for the benefit of the onclick handler:


<li style="padding-left: 15px;">
    <script src="/mo/javax.faces.resource/jsf.js.jsf?ln=javax.faces&amp;stage=Development"
          type="text/javascript">
    </script>
    <a class="selected"
       href="#"
       id="j_idt20:j_idt22:24:j_idt30:0:_t32"
       onclick="mojarra.jsfcljs(document.getElementById('j_idt20'),{'j_idt20:j_idt22:24:j_idt30:0:_t32':'j_idt20:j_idt22:24:j_idt30:0:_t32'},'');return false"
       title="Overview">
        <span id="j_idt20:j_idt22:24:j_idt30:0:_t33">&gt; Overview</span>
    </a>
</li>